The exact positioning of a body such as a projectile or an autonomic vehicle relative to an optically reflecting or partly reflecting surface is of major importance for determining the timing of detonation and for optimizing its performance when actuated.
Common methods for proximity detection utilize optical time of flight range finders, located in a projectile head, where repetitively pulsed laser radiation, emitted from the transmitter, located in the projectile head, impinges on a solid target surface. Travel time is measured by a receiver containing fast detectors located in the projectile head, measuring the reflection time of arrival and calculating the distance. These methods are suitable for distances greater than a few meters, and their accuracy is in the range of about one meter. When the sought-after distances are in the range of tens of centimeters to a few meters, these methods reach their capability limit, requiring a multiplicity of very short pulses having short rise times, thereby the cost of such systems is greatly increased, making this solution expensive and elaborate. The volume required to host the transmitter and receiver, as well as their energy source is large and cannot be placed in very small dimension projectiles, such as bullets, having diameters of 1 to 2 cm and about the same length.
Such bodies are referred to hereinafter as “small size bodies having small internal volume”. An optical range detector suitable for small dimension bodies should have the following properties:                1) resolution capability of a range of a few centimeters;        2) the capability to be contained in the body;        3) unaffected by sunlight or stray light;        4) able to operate independently without any communication, wire or wireless, to the body launching station, and        5) have a pre-set range for actuation.        